Coated articles such as transparent shower doors and IG window units are often heat treated (HT), such as being thermally tempered, for safety and/or strengthening purposes. For example, coated glass substrates for use in shower door and/or window units are often heat treated at a high temperature(s) (e.g., at least about 580 degrees C., more typically from about 600-650 degrees C.) for purposes of tempering.
Diamond-like carbon (DLC) is sometimes known for its scratch resistant properties. For example, different types of DLC are discussed in the following U.S. Pat. Nos. 6,303,226; 6,303,225; 6,261,693; 6,338,901; 6,312,808; 6,280,834; 6,284,377; 6,335,086; 5,858,477; 5,635,245; 5,888,593; 5,135,808; 5,900,342; and 5,470,661, all of which are hereby incorporated herein by reference.
It would sometimes be desirable to provide a window unit or other glass article with a protective coating including DLC in order to protect it from scratches and the like. Unfortunately, DLC tends to oxidize and burn off at temperatures of from approximately 380 to 400 degrees C., as the heat treatment is typically conducted in an atmosphere including oxygen. Thus, it will be appreciated that DLC alone as a protective overcoat cannot withstand heat treatments (HT) at the extremely high temperatures described above which are often required in the manufacture of vehicle windows, IG window units, glass table tops, and/or the like.
Prior art FIG. 1 illustrates a conventional technique which is described in U.S. Pat. No. 8,071,166, the disclosure of which is hereby incorporated herein by reference. As shown in FIG. 1, prior to thermal tempering, a coated article includes a glass substrate 1, a DLC layer 11, a zinc oxide release layer 117a, and an aluminum nitride (e.g., AlN) oxygen barrier layer 17b. Much of the protective overcoat 17 thickness consists of a cermet (ZnO—Zn) 117a, the rest being a dense dielectric of AlN 17b. This coated article on the left side of FIG. 1 is then subjected to heat treatment (HT) such as thermal tempering, and the protective film 17 protects the DLC layer 11 during such heat treatment and prevents the DLC from completely burning off. Following the HT, the protective film 17 is removed using a liquid as described in the '166 patent. Thus, DLC layer 11 is protected with a thermal barrier overcoat film 17 that protects the carbon based layer 11 from complete oxidation during tempering, with the protective film 17 thereafter being removed.
It has been found that the cermet (ZnO—Zn; ZnOx) 117a has a high electrochemical potential compared to stoichiometric ZnO, and is therefore thermodynamically metastable. The cermet is susceptible to humidity ingress and acts like a battery during sequences of high and low humidity/temperature. Over-extended grains of ZnO—Zn cermet are believed to create regions of high electrochemical potential which are readily attacked by water molecules to start an oxidative corrosion process of Zn to ZnO. It is believed that these problems, including a significantly chemically active surface of the layer 117a, is/are caused at least in part by the cermet 117a not being fully oxidized ZnO. Layers 117a and 17b have to survive handling and processing prior to and during the thermal tempering process. To address these deficiency caused by the (ZnO—Zn; ZnOx) 117a, it has been attempted to further protect the protective film 17 with an overlying thin polymer based flexible Temporary Protective Film (TPF), not shown in FIG. 1, that can be later peeled off.
It has been found that the stoichiometry of the ZnOx is not a dielectric, as it displays semiconducting behavior and has a polycrystalline Wurtzite structure with metallic and substoichiometric ZnOx. This material is not hard, is susceptible to water ingress, and can be scratched off easy. In order to avoid or reduce handling scratches, which would degrade the thermal protection of DLC during tempering and therefore burn the DLC, the TPF (e.g., of polyethylene for example) coated with a pressure sensitive adhesive on one side is applied over the AlN. This TPF is not available for float glass having a width of 3.21 m. Thus, when manufacturing products having a large width such as 3.21 m, two smaller TPF films are overlapped in order to cover the large width, and the overlap tends to occur in an area of the product where the glass is coated with DLC (e.g., in an approximately central area of the product). For example, TPF (e.g., Nitto TPF A7) from a big TPF roll of 2.56 m (100 inch) and from a small roll of 66 cm width can be used, with the TPF from the respective rolls overlapping on the product prior to HT.
This overlap of adjacent TPF films at the seam creates a capillary. In an attempt to avoid water penetrating into this capillary, it has been attempted to close the slit with UV-curable gel for example. However, this gel reacts with the reactive cermet (ZnO—Zn; ZnOx) in front of the tempering process, in a reaction which is promoted by water. This then yields a line of degraded DLC indicated by haze in reflection and/or burn marks where the overlap occurred. These haze and/or burn marks, which occur in the DLC following HT in areas where the overlap occurred, are detrimental and not desired by customers.
In certain example embodiments of this invention, prior to the heat treatment (HT) and prior to the deposition of the AlN inclusive layer of the protective film, there is presented a technique for transforming the cermet ZnOx to a more stable ZnOx via plasma passivation treatment. For example, the ZnO, based layer can be treated with a plasma of or including oxygen plasma, from an ion beam source(s). The ion beam treatment may be from an ion source(s) in collimated mode in certain example embodiments. Alternatively, the ion beam treatment may be from an ion source in a diffuse mode. After the ion beam treatment of the ZnOx, the barrier layer (e.g., AlN layer) is then deposited over the ion beam treated ZnOx. Surprisingly, it has been found that treating the zinc oxide inclusive release layer with plasma including oxygen (e.g., via ion beam treatment), prior to deposition of the oxygen blocking or barrier layer, improves thermal stability and/or quality of the product. For example, it has been found that the ion beam treatment of the layer comprising ZnOx reduces the concentration of OH-groups on the layer's surface and reduces the layer's surface roughness, thereby improving the layer's thermal stability and reducing the likelihood of the undesirable burning. Following and/or during heat treatment (e.g., thermal tempering, or the like) the protective film may be entirely or partially removed.
Example advantages include one or more of: (i) reduced or elimination of burn marks where the TPF overlap occurred; (ii) improved thermal and/or humidity stability of the protective film; and (iii) easy removal of the protective film after thermal tempering.
In certain example embodiments of this invention, there is provided a method of making a coated article, the method comprising: depositing a release layer comprising zinc oxide on a glass substrate, wherein at least a layer comprising carbon is located between the glass substrate and the release layer comprising zinc oxide; ion beam treating the layer comprising zinc oxide with at least oxygen ions to provide an ion beam treated layer comprising zinc oxide; depositing an oxygen barrier layer on the glass substrate over the ion beam treated layer comprising zinc oxide; and wherein a protective film comprising the ion beam treated layer comprising zinc oxide and the oxygen barrier layer are for protecting the layer comprising carbon during subsequent heat treatment in order to prevent significant burnoff of the layer comprising carbon.
In certain example embodiments, there is provided a method of making a heat treated coated article, the method comprising: heat treating a coated glass substrate, the coated glass substrate comprising, prior to the heat treating, a glass substrate, a layer comprising diamond-like carbon (DLC) on the glass substrate, and a protective film on the glass substrate over at least the layer comprising DLC, wherein the protective film includes (i) a release layer comprising zinc oxide which has been ion beam treated with at least oxygen ions, and (ii) and an oxygen barrier layer, the release layer and the oxygen barrier layer being of different material; during said heat treating of the coated glass substrate with the layer comprising DLC and the protective film thereon, the protective film prevents significant burnoff of the layer comprising DLC, and wherein the heat treating comprises heating the glass substrate to temperature(s) sufficient for thermal tempering, heat strengthening, and/or heat bending; and exposing the protective film to a release liquid and removing at least part of the protective film during and/or after said heat treating.
In certain example embodiments of this invention, there is provided a coated article comprising: a glass substrate supporting a coating, the coating comprising moving away from the glass substrate: a layer comprising diamond-like carbon (DLC); a layer comprising zinc oxide (e.g., which may be ion beam treated), wherein a concentration of OH-groups at a surface of the layer comprising zinc oxide farthest from the glass substrate is no greater than about 40%; and a layer comprising aluminum nitride on the glass substrate over and directly contacting the layer comprising zinc oxide.